It is known to directly attach solder bumps on integrated circuit components to bond pads on a printed circuit board or other suitable substrate to form solder bump interconnections. A gap is formed between the integrated circuit component and the printed circuit board. The solder bump interconnections extend across the gap to physically attach the component to the board and to electrically connect an electrical circuit on the component to an electrical circuit on the substrate. Solder bump interconnections are susceptible to corrosion and to cracking caused by thermally induced stresses. The gap is filled with a polymeric encapsulant material to encapsulate and strengthen the solder joints without affecting the electrical connection.
In the event that an assembly needs repair, it may be necessary to remove and replace the component. The component may be removed by grinding to expose the encapsulant and the solder bump interconnections on the board. A replacement integrated circuit component is then placed onto the printed circuit board and reflowed to connect the solder bumps. After reflow, the replacement component is underfilled with additional encapsulant that is subsequently cured. The additional encapsulant increases the distance of the component from the substrate and decreases clearances between the component and a housing holding the assembly, thereby degrading the reliability of the assembly. Further, residue on the board from grinding may reduce adhesion of the additional encapsulant. Further, grinding can damage other components on the board, such as oscillators that are sensitive to high frequency vibrations.
Another method proposed to remove a defective integrated circuit component from a printed circuit board requires immersion of the printed circuit board into a heated solvent bath to dissolve the encapsulant. After the encapsulant is removed, the microelectronic assembly is heated to a temperature sufficient to reflow the solder bump interconnections, which allows the component to be removed from the printed circuit board. However, the heated solvent bath may adversely affect other polymeric material on the printed circuit board, requiring additional repair of other components.
Therefore, a need exists for a microelectronic assembly that comprises an integrated circuit component that is underfilled with an encapsulant that is readily removable to permit removal of a defective component and to provide a clean site for attaching a replacement component. It is desired to provide a single operation that removes the component and the encapsulant. Further, there is a need for an encapsulant that allows a single component to be replaced without damaging or affecting other components or encapsulant on the substrate.